Keystone correction is provided in order to correct an image being projected by a projection system, which would otherwise be distorted principally due to an angle of projection from the projection system to the projection screen.
Typically, keystone correction is applied to a projection system so as to obtain a homography transformation that results in good image fidelity between a source image and a projected image. When the projection system includes multiple projectors in a projector array, the homography transformation is ordinarily derived for a single object, regardless of the number of objects actually formed by the projection system.
A more detailed description of a typical keystone correction is provided in “Smarter Presentations: Exploiting Homography in Camera-Projector Systems”, R. Sukthankar, et al., Proceedings of International Conference on Computer Vision (2001) and in “A Self Correcting Projector”, R. Raskar, et al., Mitsubishi Electric Research Laboratories, Inc. (2001).